Solid-state photonic components have provided a number of improvements in light efficiency for both light emission and detection. As a result of continued developments in Light Emitting Diode (LED) technology, LEDs have emerged as the preferred light source in a number of applications. Among benefits of solid-state lighting (SSL) using LED sources are long life and durability, energy savings per lumen, good quality light output, low heat, and compact size.
As LEDs continue to supplant conventional light sources in large-scale illumination applications such as high-bay lighting, developers and manufacturers have recognized some of the shortcomings and constraints related to solid-state light emission. In order to provide high-output lighting, for example, it is recognized that operating current of the LEDs can make a significant difference in light efficiency. Improved efficiencies for LED emission are typically obtained by powering the LEDs below their rated nominal component current capacity. However, reduced current, while improving efficiency, leads to lower light output per LED, resulting in the requirement to increase the quantity of LEDs in order to achieve a required light output. In some applications, the available surface area of the lighting system for mounting LEDs may be the practical limit to system efficiency.
Solid-state LEDs having a planar output surface can be the preferred option where high-density packaging is needed to provide high levels of light. These devices can include surface mounted devices (SMDs) such as the LUXEON™ 3030 LED from Lumileds Holding B.V., San Jose, Calif., for example.
Surface-mounted LEDs typically exhibit a highly Lambertian optical distribution. This means that a substantial portion of the generated light exits the flat LED emission surface at relatively high angles. Without proper correction, the light emitted at such high angles can be a source of undesirable glare. Typically, individual lenses are paired with each LED package to redirect high-angle light for a more useful optical distribution. Lens sizes exceed LED package sizes; thus, the lens ultimately determines the maximum allowable LED density and, therefore, constrains the efficiency of the lighting system. It advantageous to have lens designs that are as small and efficient as possible to increase the efficiency of lighting systems using LEDs. Improvements in light handling, such as in more effective management of incident light angles, can also be advantageous for photonic components designed to detect light as sensors, such as detectors, detector arrays, CCD (charge-coupled device) arrays, and the like. Light at high incident angles can be more difficult to detect or may be incident on a neighboring sensor, resulting in unwanted crosstalk.
Thus, it can be appreciated that there would be benefits to light management solutions that improve light efficiency for surface-mounted photonic emission and detection components.